During manufacture of a fuel injection system for an engine it is customary to assign trim data to individual injectors to compensate for fueling and timing variations. The trim data (e.g. valve timing offset, nozzle flow offset etc.) is acquired during injector testing and currently is imprinted on the injector surface as a bar-code or dot-code.
During assembly of the injectors into the engine, the bar-code or dot-code is scanned (by either a human operator or by an automated scanning system) and uploaded into the engine control unit (ECU) where the trim information is used to correct the injections.
Relying on the scanning of a code in order to load the trim data into the ECU raises the possibility that an injector could be installed without loading corresponding trim data or even the possibility that a new injector is installed during a repair/service without scanning its code. In this latter case old trim data corresponding to the original (and now replaced) injector would be applied by the ECU to the new injector with adverse effects on exhaust emissions.
In addition to the above issues it is noted that emissions regulations (e.g. the proposed California Code Regulation 1962.2 (OBDII)-(f)(15.2.2)(F) Comprehensive Output Components) may require that tolerance compensation features (e.g. trim data) implemented in hardware or software during production or repair procedures shall be monitored to ensure the proper compensation is being used. It may further be a requirement that an engine system be able to detect when the compensation being used by the control system does not match the compensation designated for the installed component.
One possible solution to the above issues would be to manufacture components having design tolerances that were extremely accurate. This method would essentially eliminate the need for trim data (and by association the need to monitor trim data) because the components would be essentially identical. However, although such an approach might overcome the above issues it would almost certainly be prohibitively expensive to implement.
It is therefore proposed to integrate an electronic ID chip into the injector with a unique identity number. This can then be checked by the ECU to ascertain if the injector has been changed. A further possibility is that the trim data may be stored in the ID chip and read by the ECU.
If an ID chip is integrated into an injector then for convenience it would be desirable to communicate with the chip using the existing injector drive wires and furthermore using the existing injector drive and diagnostic circuitry. However, where injectors are grouped into banks with a common connection, it may become necessary for each ID chip to be associated with its own unique bus address (because otherwise isolating the communication to a single injector would not be possible since all injectors on the bank would see the same signal).
If each injector requires its own bus address then it would become necessary to connect the injectors individually during assembly into the engine and instruct the ECU which injector is associated with which cylinder. This point becomes important if trim data is included in the ID chip because the ECU will need to know which cylinder it needs to apply the various trim data it stores to. However, this is not an ideal method as it is open to operator error.
EP0868602B1 discloses the use of an EEPROM device for storing trim data in an injector. However, no indication of how the data is read is mentioned other than an ‘EEPROM reader’.
WO2008/128499A1 also discloses the use of an EEPROM device for storing trim data in an injector. Communication with the EEPROM is via an HF carrier wave superimposed on the injector wires with AM or FM modulation/demodulation at each end of the injector wires. Each injector uses a pair of wires for the carrier wave signal which requires individual modulation/demodulation circuits in the ECU as well as the injectors. The disclosure does not discuss how banked injectors are addressed.
It is therefore an object of the present invention to provide an injection system that overcomes or substantially mitigates the above-mentioned problems.